<html>
    <head>
        <script type="text/javascript">
            var xmlhttp;
            function loadXMLDoc(url, cfunc) {
                if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
                    xmlhttp = new XMLHttpRequest();
                } else {// code for IE6, IE5
                    xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
                }
                xmlhttp.onreadystatechange = cfunc;
                xmlhttp.open("GET", url, true);
                xmlhttp.send();
            }
            function myFunction() {
                loadXMLDoc("a003_test.txt", function() {
                    if (xmlhttp.readyState === 4 && xmlhttp.status === 200) {
                        document.getElementById("myDiv").innerHTML = xmlhttp.responseText;
                    }
                });
            }
        </script>
    </head>
    <body>
        <div id="myDiv"><h2>Let AJAX change this text</h2></div>
        <button type="button" onclick="myFunction()">通过 AJAX 改变内容</button>
    </body>
</html>
